1. Technical Field
The present invention relates to a battery controller which controls a battery.
2. Related Art
In the related art, electric power vehicles such as hybrid vehicles or electric vehicles are mounted with a high-voltage battery that stores power for driving a traveling motor. A lower limit state-of-charge and an upper limit state-of-charge of use are set in a battery, and input/output of a current (charging/discharging) is performed such that the battery is used with the state of charge between the lower limit and the upper limit. The reason is that the battery becomes an overcharge state in a case of exceeding the upper limit state-of-charge of use, the battery becomes an over-discharge state in a case of being below the lower limit state-of-charge of use, and performance of the battery deteriorates even in any case.
For example, a technique is disclosed in Japanese Unexamined Patent Application Publication No. 2013-198300 in which when a secondary battery is charged with a constant voltage, if the secondary battery is determined to be fully charged based on a voltage value and a value of a current flowing in the secondary battery and an ambient temperature of the secondary battery is equal to or higher than a predetermined temperature, constant voltage charging is continuously performed, and if the ambient temperature of the secondary battery is lower than the predetermined temperature, the constant voltage charging is stop, thereby preventing the overcharge.
In addition, a technique is disclosed in Japanese Unexamined Patent Application Publication No. 2012-249455 in which a power supply and a battery are connected to each other when a voltage of the battery is lower than a threshold value, and the power supply and the battery are disconnected from to each other when the voltage of the battery is higher than a predetermined value determined higher than the threshold value, thereby suppressing deterioration of the battery caused by the overcharge.
In general, a state of charge (SOC) of the battery is calculated based on a voltage value of a battery, but a correct calculation of the SOC becomes difficult when malfunction occurs in a voltage detector that detects a voltage of the battery.
For this reason, when the malfunction of the voltage detector occurs and the correct calculation of the SOC becomes difficult, it is also considered to immediately prohibit the use of the battery in order to protect the battery.
In a case where the battery is used as a power supply for driving the electric power vehicle, however, it is expected that a disadvantage of the user increases when the vehicle is suddenly unavailable.
Since it is considered to have great influence on the battery and surroundings thereof in a case where the battery becomes an overcharge state compared that the battery becomes an over-discharge state, a method is also considered in which only the output from the battery is permitted and the electric power vehicle continuously travels when the malfunction occurs.
However, for example, when the malfunction occurs in a state where the SOC is low, power in the battery may be exhausted before the arrival at a vehicle repairer or the like.
The invention has been made in view of such circumstances, and an object thereof is to provide a battery usable in an appropriate range when malfunction occurs in a voltage detection unit of the battery.